84 THE COLOURS OF ANIMALS 



Variable Protective Resemblance in Reptiles 



The power of Variable Protective Eesemblance is 

 therefore present among fish and Amphibia, but the 

 most remarkable and well-known example is afforded 

 by a reptile, the Chamaeleon. The rapidity with 

 which the change of colour takes place, and the wide 

 range of tints which the animal has at its command, 

 have caused this lizard to be regarded as a type of 

 everything changeable. But the same power is also 

 present in certain of the South American lizards- 

 belonging to the family Iguanidce, and it is probable 

 that Variable Protective Eesemblance is much more 

 common than has been generally supposed. 



The changes of colour depend upon the eye 



The physiological mechanism by means of which 

 these rapid changes of colour are effected has been 

 investigated by Lister in this country, by Briicke in 

 Germany, and by Pouchet in France. At first sight 

 it appears likely that the light may directly determine 

 the distribution of colouring matter in the pigment 

 cells in or immediately beneath the skin. Each of 

 the various surroundings of an animal would, accord- 

 ing to its colour, reflect light of a certain constitution, 

 and it might well be supposed that each kind of re- 

 flected light would produce a different effect upon the 



